1. Field of the Invention
The present invention relates, in general, to the area of heating, ventilating and air-conditioning systems including the elevated components through which air is supplied to a space to be ventilated and also returned to the system. More specifically, this invention relates to ceiling-mounted concentric air diffuser plenums for use with a climate control system.
2. Description of Related Art
Climate control systems such as heating, ventilation and air-conditioning systems (HVAC systems) are often utilized in buildings to provide a comfortable climate within the building. Some buildings utilize ducts within the building to direct air from a climate control unit to specific locations for further distribution throughout a desired space. Other buildings may utilize multiple climate control units in a system in an effort to minimize the length and quantity of ducts within the building. In some buildings, especially buildings of a commercial nature, the climate control system, often comprising a number of climate control units, is mounted on the roof. Preferably the roof is a flat roof immediately above a living or working space, although the air diffuser plenum of the preferred embodiments could be utilized in conjunction with pitched roofs and/or ductwork.
Concentric diffusers are useful to provide a single diffuser housing to supply ventilation to a space while also allowing for return air to be returned to the HVAC system. Typically supply air is provided through at least one inlet into the diffuser from the HVAC outlet to the diffuser vents, or outlets, while return air is returned through at least one return outlet of the diffuser to the HVAC system. Concentric air diffusers are often mounted in drop ceilings to minimize the number of locations for vents in ceilings since one diffuser may be used for both supply and return air.
One problem with typical concentric diffusers is the imprecise flow of air from different portions of the diffuser. Specifically, in a drop box type diffuser where air is supplied to a space through four lateral sides of the diffuser, manufacturers often advertise a particular cubic feet per minute of air distribution from the diffuser. For instance, for a 5-ton HVAC unit with 18 inch supply ducting and side vents twice the length of the end vents, the manufacturer may advertise a total of 2,000 cubic feet per minute supplied from the diffuser: 500 cfm from each end and 1,000 cfm from each side. In actuality, the diffuser may supply 875 cfm from a side and 825 cfm from an end at velocities at specific locations including 1750 feet per minute at a location along the end closest to the supply inlet of the diffuser while as little as 600 feet per minute at a portion of the opposite end. Thus, the supplied air is imbalanced.
Some manufacturers advertise that baffles may need to be installed after installation of the diffuser in order to balance air flow at that time. The problem with this method of balancing air flow is that with the diffuser installed with a ceiling, access may only be obtained at and through the vents since the top shroud often extends into the ceiling. In order to balance air flow some technicians may shut portions of the slats in the vents while opening other vent slats to a further degree. Unfortunately, when a vent slat is moved closer to the closed position, it may tend to vibrate and make more noise due to the relatively large amount of air attempting to rush through narrower openings in the vent. If the vents do not have moveable slats, then other methods may be necessary.
Accordingly, a need exists to provide balanced air flow out of a concentric diffuser without requiring measurements or adjustment of air flow after installation.
Another need exists to provide an internal baffle system which does not add additional noise to a diffuser.
Another need exists to provide a relatively inexpensive means for providing balanced air flow without requiring special measuring equipment or skills on the part of an operator.
It is therefore desirable to provide an improved concentric air diffuser.
Furthermore, a need exists for a more efficient air diffuser capable of more precisely directing air than has been known in the prior art.
It is therefore desirable, to have an improved air diffuser plenum.